Oxidation is one of the fundamental reactions in organic synthesis. Importantly, sulfoxidation receives special attention in the pharmaceutical chemistry since many sulfoxides are present as active pharmaceutical ingredients. Sulfoxides also act as intermediates for various organic reactions. Sulfoxidation can be achieved using peracids or halogen derivatives as oxidants in an organic medium. However, this method involves using stoichiometric oxidants that generally produce undesirable side products, usually originating from the oxidants.
Sulfoxidation can also be achieved using hydrogen peroxide as an oxidant in an organic medium. This method involves using environmentally benign hydrogen peroxide along with several transition metals. However, the use of low volatile organic solvents as a reaction medium makes it less attractive due to the environmental factor and cost. Sulfoxidation can further be achieved by using hydrogen peroxide as an oxidant in an aqueous medium.
The use of hydrogen peroxide provides an alternative environmentally friendly process that uses water as a reaction medium. Transition metal catalyzed reactions in a pure aqueous medium with hydrogen peroxide as an oxidant makes the methodology attractive in the development of “Green Chemistry” processes. However, the drawback of this method is the difficulty in designing stable catalysts that are soluble in water. Hence, there is an unmet need to develop simple, cost effective, and environment friendly sulfoxidation catalysts that function in an aqueous medium.